Regulator device for electric current



April 4, 1961 s. VERNET ETAL 2,978,665

REGULATOR DEVICE FOR ELECTRIC CURRENT Filed July 11, 1956 INVENTOR Sees/us Vsmver 5y GEORGE AsAK/Ju/A 5mm, 0mm [my/W4;

regulating function,

partially conductive material 12.

mid-States tent REGULATOR DEVICE FOR ELECTRIC CURRENT Sergius ,Vernet and George Asakawa, Yellow Springs, Ohio, assignors, by direct and mesne assignments, to Antioch College, Yellow Springs, Ohio, a corporation of Ohio Filed ul 11, 1956, Ser. No. 597,292 6 Claims. (Cl. 338-223 load, thereby preventing any overload condition from existing for any substantial period of time,

(4) The device is responsive to ambient temperature and/or'current input for the performance of its current- The device automatically increases its resistance to current'fiow with increasing temperature before a maximum temperature is reached; thereby choking off the current before it becomes excessive and giving a very sensitivecurrent control action with a minimum fluctuation in current flow. I

Otherobjects of thisinvention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in i the several views.

In the drawings: I

Fig. '1 is anelevational view of one embodiment of the invention.

' Fig. 2 is a plan view of'the Fig. l embodiment.

. Fig. 3 is an enlarged sectional view on line 3--3 in to be understood that the invention is not limited in its application to the details of construction and arrange .ment of parts illustrated in the accompanying drawings,

since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also,

'it is to be understood'that the phraseology or terminology employed herein is for thepurpose of description and not of limitation;

In the drawings' there'is shown a current regulating device 2 including two spaced electrodes 4 and 6. Each of electrodes 4 and 6 includesa circular disk 8 and a rod 10, both being formed of brass or other metal having the ability to conduct electric current.

Between disks 8 there is secured a disk or wafer of The term partially conductive is used to indicate a material wherein a portion of the material is conductive and another portionis non-conductive. Material 12 preferably comprises finely divided conductive particles dispersed in a mixture of (l) thermally expansible, non-conductive materialand 2) material preventing flow of the expansible material from' b'etweenthe electrodes in the transition temperature range of'said expansible material.

The purpose of the finely divided conductive particles is to impart a degree of electrical conductivity to material 12 by forming a number of conductive paths through said material. The conductive particles may be formed of different materials, as for example carbon, a metal such as copper or aluminum, silicon, silicon carbide, lead sulfide, iron sulfide, or molybdenum sulfide.

The purpose of the thermally expansible, non-conductive material is to (1) spread the conductive particles apart as the temperature of material 12 is increased, and (2) thereby increase the resistance of material 12 to current flow. The thermally expansible, non-conductive material may be formed of different materials, as for example waxes, parafiin, polyethylene or polysiloxane. The term thermally expansible material will be understood to refer to a material which undergoes a substantial increase in its volumetric displacement when its temperature is increased. The term non-conductive Will be understood as being used in a relative sense to indicate a material having substantially greater resistance to current flow than the dispersed conductive particles, it being appreciated that the non-conductive" material conducts small quantities of electricity but offers a higher resistance to its passage than the conductive particles.

The purpose of the flow-preventing material is to contain the 'expansible material when it is in a liquid or semi-liquidistate, as when it has undergone a transition from a lowtemperature contracted condition (in the solid state) to a higher temperature expanded condition (in the liquid or semi-liquid gel state). The flow-preventing material may, be formed of different materials, as for example rubber; a high melting plastic such as polytetrafluoroethylene, polymonochlorotrifiuoroethylene, polyadipamide, polyvinyl chloride or acrylonitrile resin; or a high melting wax. The term high melting as used herein refers to a material which is solid in the transition temperature range of the thermally expansiblemateri-al, i.e. a material which'changes from a solid to a liquid at a temperature above the transition temperature range of the expansible material.

Preferably the volumetric proportions of the component materials making up material 12 are about 40% conductive particles, 40% thermally expansible material and 20% flow-preventing material.

Mixing of the component materials together can be effected on a two-roll rubber mill. The product emerges from the rubber mill as a sheet of material. When relatively rigid materials such as polytetrafluoroethylene and polyethylene are used ascomponent materials the sheet of material is pulverized in a hammer mill and subsequently compressed into the desired wafer shape by suitable molding mechanisms. When relatively soft materials are used as components for material 12 the hammer mill operation can be omitted. Wafer 12 is secured against the inner faces of disks 8 by conventional bonding agents.

Operation of the illustrated device is such that when rods 10 are connected into an electrical circuit and the temperature of material 12 is relatively low the conductive particles are quite close together so as to form a great number of conductive paths through material 12. As the temperature of material 12 is increased (due to the passage of electric current and/or an increase in ambient temperature) the thermally expansible material expands. As the temperature nears and reaches the transition range of the expansible material there is a proportionately large increase in the volume of material 12, which spreads the conductive particles apart and causes a large increase in scrapes disks 8 occupying substantially the Fig. 3 dotted line position at full expansion. The precise positions of disks 8 are of course determined by the expansion characteristics of the expansible material and the relative amount of expansible material employed.

When the device is positioned in an atmosphere having changing temperature characteristics an increase in the ambient temperature will heat material 12 so as to expand the expansible material and thereby increase the resistance to current flow. In this way the current or wattage through the device can be controlled in accordance with the ambient atmosphere temperature. By proper choice of the expansible material it is possible to regulate the current in many temperature ranges. Also, the choice of expansible material may be used to determine the width of the range, from a few degrees to a wide range.

"When the device .is operated by electric current (as distinguished from ambient temperature) an increase in the input wattage willheat material 12, and the resultant increase in resistance will tend to choke off the current before a maximum temperature is reached. As a result the heating" capacity of the current is reduced and the temperature of material 12 is decreased so as to contract the expansible material and thereby establish an equilibrium current through the device. The character of the expansible material, particle size of the conductive particles, and the proportions of component materials will determine the current carried.

The above described choke ofilaction is in contrast to that of a conventional fuse wherein no increase in resistance is experienced until the fuse material melts. .By reason of the choke off action there is less wattage fluctuation because the resistance of the device is constantly changing to meet changingcurrent conditions/1t will also be understood that there is usually no off position of the device in the sense that current flow through the device is completely stopped. A certain amount of current is always free to flow through the device. a f i It will be noted that the diameter of wafer 12 is relatively large compared to its thickness. As a result the expansible material is very quickly enabled to expand and contract in response to changes in the temperature of material 12. When the device is operated by electric current the current is enabled to spread over the entire extent of disks 8 so as to subsequently travel through all portions of material 12. The small thickness of wafer 12 (preferably about .050 inch) gives relatively short current paths and thereby allows changes in current flow to be reflected almost immediately in volumetric changes of material 12. a

When the device is operated by ambient temperature changes disks 8 act to transfer heat between material '12 and the ambient atmosphere. The surface area of the disks is relatively large for the volume of material 12, and the heat transfer action is very rapid. Thisrapid heat transfer action contributes to the prevention of any undesired wattage variation by enabling quick volumetric change of material 12.

During the expansion andcontraction of material 12 the flow-preventing material must have a slight movement in accordance with the movement ofthe expansible material. However this movement is so slight that conventional plastics, waxes and rubbers can be employed .asfiow-preventing materials without difiiculty. The use of a mixed-in flow-preventing material is advantageous by reason 'of its extremely low cost. However it is contemplated that the flow-preventing materials could be distributed around the periphery of wafer 12 in order to perform the flow-preventing or sealing function. Also a rubber sleeve or rubber coated fabric sleeve or other non-conductive sheathing can be connected between the peripheral edges of disks 8 to perform the (sealing" function.

We claim:

1. A current regulator comprising spaced electrodes; and partially conductive material therebetween; said material comprising finely divided carbon particles dispersed in a mixture of polyethylene and polytetrafluoroethylene; said polytetrafluoroethylene preventing flow of the polyethylene from between the electrodes in the transition temperature range of said polyethylene; whereby, during the passage of an electric current between the electrodes the carbon particles are caused to heat and expand the polyethylene so as to increase the spacing between adjacent ones of the carbon particles in such manner as to control the current flow through the partially conductive material.

2. A current regulator comprising spaced electrodes; and partially conductive material therebetween; said material comprising 40 volumetric parts finely divided carbon particles dispersed in a mixture of about 40 volumetric parts polyethylene and 20 volumetric parts polytetrafluoroethylene, said polytetrafluoroethylene preventing flow of the polyethylene from between the electrodes in the transition temperature range of said polyethylene; whereby, during the passage of an electric current between the electrodes the carbon particles are caused toheat and expand the polyethylene so as to increase the spacing between adjacent ones of the carbon particles in such manner as to control the current flow through the partial ly conductive material.

3. A current regulator comprising two parallel'electrically conductive disks spaced apart about .050 inch to'form spaced electrodes; and partially conductive material in the space therebetween; said material comprising solid finely divided electrically conductive particles dispersed ina mixture of (l) softenable thermally expansible non-conductive material and (2) solid non-com ductive flexible material preventing flow of the expansible material from between the disks in the transition temperature range of said expansible material; whereby, during the passage of an electric current between the disks the conductive particles are caused to heat the expansible material so as to increase the spacing between adjacent ones of the conductive particles in such manner as to control the current flow through the partially conductive material.

4.'A current regulator comprising spaced electrodes; and partially conductive material therebetween; said material comprising solid finely divided electrically conductive particles dispersed in a mixture of (l) softentable thermally expansible non-conductive polyethylene and (2) solid non-conductiye flexible material preventingflow of the expansible material from'between the electrodes in the transition temperature range of said expansible material; whereby, during the passage of an electric current between the electrodes the conductive particles are caused to heat the expansible material so as to increase the spacingbetween adjacent ones of the conductive particles in such manner as to control the current flow through the partially conductive materiaL' -,5. A current regulator comprising spaced electrodes; and partially conductive material therebetween; said material comprising solid finely divided electrically conductive particles dispersed in a mixture of (1) softenable -thermally expansible non-conductive 'materialand (2) solid non-conductive polytetrafluoroethylene preventing flow of the expansible material fi'om' between the electrodes in the transition temperature range of said expansible material; whereby, during the passage of an electric tive particles dispersed in a mixture of (1) softenable thermally expansible non-conductive material and (2) solid non-conductive flexible material preventing flow of the expansible material from between the electrodes in the transition temperature range of said expansible ma terial; whereby, during the passage of an electric current between the electrodes the conductive particles are caused to heat the expansible material so as to increase the spacing between adjacent ones of the conductive particles in such manner as to control the current flow through the partially conductive material; said flow-preventing material being selected from the group consisting of rubber and polytetrafluoroethylene.

6 References Cited in the file of this patent UNITED STATES PATENTS Benkelman Oct. 3, 1933 Ruben May 1, 1945 Edgar et al. Oct. 2, 1945 Brubaker et al. May 14, 1946 DAlelio Sept. 10, 1946 OTHER REFERENCES pages 103107. 

1. A CURRENT REGULATOR COMPRISING SPACED ELECTRODES, AND PARTIALLY CONDUCTIVE MATERIAL THEREBETWEEN, SAID MATERIAL COMPRISING FINELY DIVIDED CARBON PARTICLES DISPERSED IN A MIXTURE OF POLYETHYLENE AND POLYETETRAFLUROETHYLENE, SAID POLYTETRAFLUOROETHYLENE PREVENTING FLOW OF THE POLYETHYLENE FROM BETWEEN THE ELECTRODES IN THE TRANSITION TEMPERATURES RANGE OF SAID POLYETHYLENE, WHEREBY, DURING THE PASSAGE OF AN ELECTRIC CURRENT BETWEEN THE ELECTRODES THE CARBON PARTICLES ARE CAUSED TO HEAT AND EXPAND THE POLYETHYLENE SO AS TO INCREASE THE SPACING BETWEEN ADJACENT ONES OF THE CARBON PARTICLES IN SUCH MANNER AS TO CONTROL THE CURRENT FLOW THROUGH THE PARTIALLY CONDUCTIVE MATERIAL. 